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5. Connecting to the bus
5. 1. Wiring recommendations
• Use Telemecanique-approved cables and wiring accessories to ensure good transmission quality (matched impedance, immunity,
shielding connection, etc.).
• Keep the Modbus cable away from the power cables (30 cm minimum).
• Be sure to cross the Modbus cable and the power cables at right angles.
• Whenever possible, connect the bus cable shielding to the protective ground, e.g., to the ground of each device if this ground is connected
to the protective ground.
• Install a line terminator at both ends of the line.
• Ensure the correct line polarization.
• Connect the common polarity ("Common" signal) to the protective ground at one or more points on the bus.
For more information, please refer to the TSX DG KBL E guide: "Electromagnetic compatibility of industrial networks and fieldbuses".
5. 2. Modbus RS485 standard
The characteristics and accessories mentioned in this section ("5. Connecting to the bus") comply with the Modbus standard.
Other non-Modbus-standard RS485 wiring diagrams are possible. Please see the Appendix for further information.
The latest generation of Telemecanique equipment conforms to Modbus (2-wire RS485).
Main characteristics:
Maximum length of bus 1000 m at 19,200 bps
Maximum number of stations 32 stations, i.e., 31 slaves (without repeater)